by chance I got hold of a NUCLEO-H753ZI board. Using STLINK V2J28M18, I can read memory and flash as expected. But reading system memory at 0x1ff00000 gives "Device Memory not accessible". As another indications, I can't get any of the bootloaders to react, e.g. dfu by shorting CN1 Pins 5 and 7 and connecting a USB to CN13.
I don't see anything bootloader related in the errata sheet ES0392 Ver. 1. Do I do anything wrong, is my single chip broken or is there a problem with bootloader on STM32H743 Rev. Y?